We picked up a Thule hitch-mounted box from the LL Bean clearance centre in North Conway last summer, and used it for the first time last month. 
http://www.thule.com/en-us/us/products/carriers-and-racks/boxes-and-baskets/rear-mounted-cargo
It worked great with the newly installed Rocky Mountain Westy 2" receiver.  My only note was that the tail-lights on the box are a bit dim - not sure if that's Thule's problem or the tail-light adaptor in the van, but am looking for replacement LED  bulbs to 'lighten' up the rear.  

The taillights on the Thules box I consider essential - a hitch-mounted carrier is otherwise obscuring your taillights mostly or completely.

James
Ottawa ON
'91 Weekender

> Date: Sun, 7 Jun 2015 00:55:46 -0300
> From: RNicholl@NBNET.NB.CA
> Subject: Re: Extra storage?
> To: vanagon@GERRY.VANAGON.COM
> 
> Jeff:
> 
> I do not care for the hitch-mounted carriers, but if you do get one, use a bag such as the Rola (http://www.amazon.ca/gp/product/B000E7WLJW?psc=1&redirect=true&ref_=oh_aui_detailpage_o05_s00).  
> 
> I used the Rola in the cargo tray over the cab on our dinosaur inspired wanderings from Calgary to New Brunswick last summer.
> 
> On 06-Jun-2015, at 22:35, Jeff Palmer wrote:
> 
> > First out of Province trip with the kids (4 and 6) this summer. We have a fair bit of gear and I'm looking for a bit more space. Options seem to be a rooftop carrier, motorcycle trailer or hitch mount cargo carrier like this:
> > 
> > http://www.princessauto.com/en/detail/53-1-2-x-19-1-2-in-aluminum-hitch-mount-cargo-carrier/A-p8547317e
> > 
> > Anyone have experience with either of the last two? 
> > 
> > Thanks
> > Jeff
> > 
> > Sent from my iPhone